1. Field of the Invention
The present invention relates to a data storage apparatus that reads and outputs data stored in a storage medium in response to a data access request from an external device. Further, the present invention relates to a data access apparatus that acquires data from an external device that stores data.
2. Description of the Related Art
In recent years, information processing apparatus such as personal computers and personal digital assistants, and digital home appliances such as digital cameras, digital video cameras, digital videodisk recorders, and digital televisions have become rapidly widespread. Furthermore, data storage media such as hard disk drives and memory cards have been increasing in capacity, as well. Generally, various contents, such as still images, video, audio, graphics, documents, presentations, spreadsheets, are distributed to and recorded in these devices. In view of this, there is a greater demand to access such contents from a certain device data stored in other devices, such as browsing contents stored in other devices via a single-function device such as a digital television, for example. Accordingly, the DLNA (Digital Living Network Alliance), for instance, has proposed rules for providing devices with a network function realized by a wireless LAN, for instance, and exchanging data between devices.
If the amount of data stored in each device becomes too large, it is difficult to read data of all the contents stored in each device at one time, and thus it is necessary to read only the necessary content data by designating conditions using functions such as retrieval and browsing. These retrieval and browsing functions are realized via a network, which increases processing time, and for example, when contents of a digital camera or a digital video camera are browsed via a digital television, a problem may occur in that responsiveness with respect to a user operation falls remarkably. In view of this, the following are known techniques to increase speed in data access via networks.
(1) In WWW browsers with which a web page is downloaded from a server and displayed, a link table is created that holds a link destination list for each web page with the selection frequency based on the past history, and pages with higher selection frequency are pre-read based on the link table (see Japanese Patent Laid-Open No. 11-024982).(2) The mechanism of totaling and analyzing a WWW data access history is provided on a proxy server, priority is given, based on the analysis result, to the data cached by a cache server, and for each requested data piece, a condition is provided for determining whether or not to pre-read the data in accordance with the priority (see Japanese Patent Laid-Open No. 11-149405).(3) A cache server records file accesses, and determines files to be pre-read based on files whose access frequency is high and intervals of updating the files, and pre-reads those files (see Japanese Patent Laid-Open No. 11-024981).(4) A cache server holds user profile information, predicts a document that will be requested next and a document similar to that document using similarity between documents, and pre-reads the documents (see Japanese Patent Laid-Open No. 2001-101061).(5) A server creates a user action model by collecting and analyzing operation history information at information reference terminals and statistical information at installation bases, and distributes the model to the information reference terminals, and the information reference terminals perform cache in advance (see Japanese Patent Laid-Open No. 2003-030037).(6) A content browsing device analyzes at least one of metadata pieces of contents displayed in list and acquisition conditions therefor, associates them with operation screen data, generates one or more acquisition conditions for acquiring the next content list, and performs pre-reading (see Japanese Patent Laid-Open No. 2007-140985).
However, with the above conventional techniques, pre-reading using link information as disclosed in (1) cannot be applied to data access to data that does not have link information, that is, to data access by designating a condition such as the order of file creation date/time. Further, to perform pre-reading using user profile information as disclosed in (4), it is necessary to construct user profile information. Further, although pre-reading using statistical information as disclosed in (2), (3), and (5) is effective in the case where the same data is repeatedly accessed, it is not effective in the case where new data is accessed or data is accessed by designating various conditions. Furthermore, although pre-reading in association with operation screen data as disclosed in (6) is effective in the processing performed by a data access apparatus, such pre-reading cannot be applied to processing performed by a data storage apparatus.